Swash plate compressor

ABSTRACT

The lubrication between a shoe and a shoe pocket is improved without having to perform a complicated forming process. In a swash plate compressor comprising a swash plate locked to a drive shaft, which rotates together with the drive shaft, a shoe  31  that slidably contacts the swash plate, a piston  13  slidably disposed within a bore defining a compression space and a shoe pocket  36  that is formed as an integrated part of the piston  13  and slidably fits with the shoe  31 , a beveled portion  41  is formed at an edge of an opening at the shoe pocket  36 . A recessed portion  40  of the shoe pocket  36  is formed so as to achieve a constant curvature, whereas a projecting portion  32  of the shoe  31  is formed so as to achieve at least two different curvatures. The shoe pocket is designed so that a tangent point  46  of the recessed portion  40  and the beveled portion  41  is set within a strip range  45  over which the projecting portion  32  and the recessed portion  40  achieve contact with each other.

DESCRIPTION

This application is a U.S. National Phase Application under 35 USC 371of International Application PCT/JP03/14566 filed Nov. 17, 2003.

TECHNICAL FIELD

The present invention relates to a swash plate compressor to be used ina cooling cycle or the like and more specifically, it relates to astructure to be adopted in an area where the swash plate is connectedwith piston.

BACKGROUND ART

In an example of the related art adopted in the area where the swashplate is connected to the piston in a swash plate type compressor, arecessed ball receiving portion at a shoe is made to contact the ballonly at an intermediate position along the direction of the depth of therecessed ball receiving portion, to form a sealed oil reservoir voidspace next to the ball under the contact position and to form a narrowclearance that opens to the outside next to the ball above the contactposition and a through hole formed so as to pass through thecircumferential wall of the shoe toward the oil reservoir void space(see Japanese Unexamined Utility Model Publication No. S 54-38913). Thisstructure is considered to facilitate the supply of lubricating oil tothe oil reservoir void space and to the narrow clearance and thusimprove lubrication at the sliding portions.

In another example of the related art, at a shoe having a semisphericalprojecting portion, a semispherical convex surface which slides againsta semispherical concave portion formed at a piston with a projectingsurface of a rotating body resulting from the rotation around the axisof the shoe is formed with a circular arc drawn around a center offsetfrom the axis of the shoe by a specific distance along the directionperpendicular to the axis (see Japanese Unexamined Patent PublicationNo. 2001-248547). The clearance created between the semispherical convexportion on the top side of the shoe and the semispherical concaveportion by adopting this structure allows the lubricating oil to besupplied with ease to achieve an improvement in the lubrication at thesliding portions.

In the art disclosed in Japanese Unexamined Utility Model PublicationNo. S 54-38,913 mentioned above, gaps (i.e., the oil reservoir voidspace and the narrow clearance) are formed between the ball and therecessed ball receiving portion by allowing the recessed ball receivingportion to have a specific curvature which is different from that of aperfect sphere, as illustrated in FIGS. 2 to 4 in this publication 1. Inthe art disclosed in Japanese Unexamined Patent Publication No.2001-248547, on the other hand, the void where the lubricating oil iscollected is formed by adjusting the curvatures of both the shoe and thesemispherical concave portion to predetermined degrees. However, thereis a problem in that it is difficult to form a shoe pocket that isequivalent to the recessed ball receiving portion or the semisphericalconcave portion described above and it therefore necessitatesconsiderable technical expertise and high production costs to form theshoe pocket with an adjusted curvature such as that described above inreference to the related art.

Accordingly, an object of the present invention is to improve thelubrication between the shoe and the shoe pocket without necessitating acomplicated forming process.

DISCLOSURE OF THE INVENTION

In order to achieve the object described above, the present inventionprovides a swash plate compressor comprising a swash plate fixed to adrive shaft, which rotates together with the drive shaft, a shoe thatslidably contacts the swash plate, a piston that is slidably disposedinside a bore defining a compression space and a shoe pocket that isformed as an integrated part of the piston and slidably fits with theshoe, characterized in that a beveled portion is formed at an edge of anopening of the shoe pocket.

In this structure, lubricating oil can be taken in with ease through thebeveled portion formed at the shoe pocket and, as a result, thelubricating oil can be supplied into a space between the shoe pocket andthe shoe in sufficient quantity to improve the slidability and the wearresistance. Furthermore, the shoe pocket edge can be beveled with easewhen forming and machining the shoe pocket and there is anotheradvantage achieved by forming such a beveled portion in that it inhibitsformation of a burr at the shoe pocket edge.

In addition, it is desirable that a recessed portion of the shoe pocket,at which the shoe is received, be formed so as to achieve a specificcurvature, that a projecting portion of the shoe, which faces oppositethe recessed portion, be formed so as to achieve at least two differentcurvatures and that the tangent point at which the beveled portion andthe recessed portion achieve contact with each other be set within arange over which the projecting portion and the recessed portion achievecontact with each other.

In the structure described above, while the projecting portion of theshoe is formed to achieve at least two different curvatures, therecessed portion at the shoe pocket is formed so as to achieve aspecific constant curvature (so as to be a true sphere). This differencebetween the shapes of the shoe and the shoe pocket keeps the shoe andthe shoe pocket from achieving full contact over the entire range whenthey are fitted with each other and instead, the shoe and the shoepocket achieve contact with each other over a narrow strip when the shoeslides inside the shoe pocket as the swash plate rotates. In thestructure described above, the tangent point (tangential line) of therecessed portion and the beveled portion at the shoe pocket is setwithin the range of the strip so as to allow the lubricating oil to betaken in more efficiently through the beveled portion.

Moreover, it is desirable to constitute the beveled portion with acurved surface achieving a constant curvature which is smaller than thecurvature of the recessed portion.

Such a structure can be achieved by first machining the shoe pocket to apredetermined depth so as to achieve a spherical shape having apredetermined radius of curvature in the recessed portion and thenbeveling the end of the opening at the recessed portion so as to achievea spherical shape with a curvature smaller than that of the recessedportion (so as to achieve a larger radius). By adopting this method, theforming process is simplified.

The beveled portion may assume a shape other than that described above,and the advantages described above can be achieved with a beveledportion having a curved surface with at least two different curvaturesor with a beveled portion having a flat surface.

In addition, it is desirable that the tangential line of the recessedportion and the tangential line (plane) of the beveled portion form anangle equal to or smaller than 45° at the tangent point of the recessedportion and the beveled portion.

When the angle formed by the tangential lines is 45° or less, thelubricating oil can be held in the void space defined with the beveledportion in a desirable manner and, as a result, the lubrication isimproved even more effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the structure adopted in a swash platecompressor according to the present invention;

FIG. 2 is a partial enlargement, showing the connection of the shoe andthe shoe pocket;

FIG. 3 illustrates the characteristics of the shape of the shoe;

FIG. 4 illustrates the characteristics of the shape of the shoe pocketachieved in a first embodiment;

FIG. 5 illustrates the shoe sliding inside the shoe pocket;

FIG. 6 shows the characteristics of the shape of the beveled portionachieved in the first embodiment;

FIG. 7 shows the characteristics of the shape of the beveled portionachieved in a second embodiment; and

FIG. 8 shows the characteristics of the shape of the beveled portionachieved in the third embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

The following is an explanation of embodiments of the present invention,given in reference to the attached drawings. FIG. 1 shows a swash platecompressor 1 achieved in an embodiment, which is employed in a freezingcycle that uses a coolant as a working fluid and comprises a front-sidecylinder block (hereafter referred to as a front block) 2, a rear-sidecylinder block 3, a front-side cylinder head (hereafter referred to as afront head) 4, a rear-side cylinder head (hereafter referred to as arear head) 5, valve plates 6, intake valves 7, discharge valves 8,gaskets 9 and 10, a drive shaft 11, a swash plate mechanism 12, a piston13 and the like.

The front block 2 and the rear block 3 are linked with each other, andthe front head 4 and the rear head 5 are respectively locked onto thefront side (the left side in the figure) of the front block 2 and therear side (the right side in the figure) of the rear block 3 with bolts(not shown) so as to seal off the end surfaces of the two cylinderblocks 2 and 3. Sets, each constituted of a gasket 9, an intake valve 7,a valve plate 6, a discharge valve 8 and a gasket 10 disposed in thisorder starting from the side toward the cylinder block 2 or 3 are heldbetween the front block 2 and the front head 4 and between the rearblock 3 and the rear head 5.

The drive shaft 11 is used to communicate the driving force imparted byan engine or a motor and is inserted through and supported rotatably ata bearing hole 15 formed at the front head 4, the front block 2 and therear block 3. A plurality (e.g., five) of bores 16 are formed over equalintervals on the circumferences of the front block 2 and the rear block3 ranging around the drive shaft 11, and a double headed piston 13 isslidably disposed inside each bore 16. The piston 13 connects with aswash plate mechanism 12 to be detailed later and is allowed to makereciprocal movement. Thus, a compression space 17, the volumetriccapacity of which changes as the piston 13 moves, is defined inside eachbore 16.

Intake chambers 20 and discharge chambers 21 are defined inside thefront head 4 and the rear head 5. In the intake chambers 20, which areformed toward the centers of the cylinder heads 4 and 5 with barrierwalls 22, the coolant is guided through specific passages from alow-pressure line of the freezing cycle, and the coolant having beenguided to the intake chambers travels through the intake valves 7, thevalve plates 6, the discharge valves 8 and intake ports (not shown)formed at gaskets 9 and 10 before it is taken into the compressionspaces 17. The discharge chambers 21 which are defined further outwardrelative to the intake chambers 20 by the barrier walls 22 and an outerwall 23 are made to communicate with the high-pressure line of thecooling cycle via a specific passage. The coolant having been compressedat the compression spaces 17 travels through the discharge valves 8 setin an open state, the valve plates 6, the intake valves 7 and dischargeports (not shown formed at the gaskets 9 and 10 before it is dischargedinto the discharge chambers 21.

The swash plate mechanism 12 includes a swash plate 30 and shoes 31. Theswash plate 30 is a member assuming a substantially disk-like shape andis locked to the drive shaft 11 with the shaft locking portion 34located at a central area thereof so as to form an angle other than aright angle relative to the drive shaft 11. The shoes 31, which aresubstantially semispherical members each having a projecting portion 32and a flat portion 33, are slidably locked near an edge of the swashplate 30 with the flat portion 33 facing opposite the swash plate 30 soas to slide freely as the swash plate 30 rotates and become displacedforward/backward (to the left/right in the figure) as the swash plate 30rotates.

In addition, the pistons 13 each include shoe pockets 36 assuming arecessed shape and located at the inner wall toward the cylinder heads 4and 5 at a hollow portion 35 defined therein, as shown in FIGS. 1 and 2,and the pistons 13 each move reciprocally as the corresponding shoes 31become slidably fitted at the shoe pockets 36.

The projecting portion 32 at each shoe 31 is formed so as to achieve atleast two different curvatures and the curvature at a vertex P1 of theprojecting portion 32 is different from the curvature at another pointP2, as shown in FIG. 3. The projecting portion in the embodiment isdesigned so that when R1 represents the radius of curvature at the pointP1 and R2 represents the radius of curvature at the point P2, therelationship expressed as R1>R2 is achieved.

In addition, as shown in FIG. 4, the shoe pockets 36 are eachconstituted with a recessed portion 40 and a beveled portion 41. Theprojecting portion 32 of the shoe 31 is slidably received at therecessed portion 40, and its curvature is defined with a single circleof curvature S1. The beveled portion 41 is formed at the edge of theopening of the recessed portion 40, and has a curvature defined by acircle of curvature S2 having a larger radius of curvature than that ofthe circle of curvature S1 in the first embodiment. It is desirable thatwith r1 representing the radius of the circle of curvature S1 and r2representing the radius of the circle of curvature S2, a relationshipexpressed as r2/r1≈1.1 be achieved.

As explained above, the projecting portion 32 at each shoe 31 achieves aplurality of curvatures and the recessed portion 40 at each shoe pocket36 achieves a single curvature, and thus, a contact area 45 over whichthe shoe 31 and the shoe pocket 36 achieve contact during operation(when the piston 13 moves reciprocally) is a strip, as shown in FIG. 5.In addition, a tangent point 46 of the recessed portion 40 and thebeveled portion 41 is set within the range of a contact area strip 45and the angle α formed by a tangential line of the recessed portion 40and a tangential line b of the beveled portion 41 at the tangent point48 is set equal to or smaller than 45° in the structure, as shown inFIG. 6.

By adopting the structure described above, the beveled portion 41 formedat the edge of the opening of the shoe pocket 36 (the recessed portion40) allows the lubricating oil to be easily taken into the space betweenthe shoe 31 and the shoe pocket 36 and, as a result, better slideabilityand better wear resistance are achieved between the shoe 31 and the shoepocket 36. Moreover, by setting different curvatures at the projectingportion 32 of the shoe 31 and at the recessed portion 40 of the shoepocket 36, a void space 48 is formed between the shoe 31 and the shoepocket 36, as shown in FIG. 5 so as to collect the lubricating oil atthe void space 48 readily to further improve the lubrication. Inaddition, while the shoe 31 and the shoe pocket 36 achieve contact overthe contact area strip 45 due to the different curvatures achieved atthe shoe 31 and the shoe pocket 36, the beveled portion 41 is designedto remain within the contact area strip 45 at all times and, as aresult, the lubricating oil can be taken in effectively through thebeveled portion 41. The formation of such a beveled portion 41 achievesan added advantage in that no burr is formed during the forming process.

In the following explanation of other embodiments of the presentinvention given in reference to drawings, the same reference numeralsare assigned to components identical to or similar to those in the firstembodiment to preclude the necessity for a repeated explanation thereof.

The shoe pocket 36 shown in FIG. 7, which is achieved in the secondembodiment, includes a beveled portion 50 constituted with a curvedsurface with a plurality of different curvatures, e.g., the curvaturesat arbitrary two points P3 and P4 are different from each other. Byadopting such a structure, too, the lubrication can be improved, as inthe first embodiment, without greatly compromising the ease offormation.

A shoe pocket 36 in FIG. 8, which is achieved in the third embodiment,includes a beveled portion 55 constituted with a flat surface anddesigned so as to ensure that the angle β formed by a tangential line bof the recessed portion 40 and the beveled portion 55 at the tangentpoint 46 is equal to or smaller than 45°. By adopting such a structure,too, the lubrication can be improved, as in the first and secondembodiments, without greatly compromising the ease of formation.

INDUSTRIAL APPLICABILITY

As described above, by adopting the present invention having bevelededges at the openings of the shoe pockets, the lubrication can beimproved without complicating the forming process. In addition, byassuming specific characteristics in the shapes of the shoes and theshoe pockets and assuming a specific positional arrangement for thetangent point of the recessed portion and the beveled portion at theshoe pockets at a specific position, the lubricating oil can be taken inthrough the beveled portions with a high degree of effectiveness.

1. A swash plate compressor comprising: a swash plate locked to a driveshaft, which rotates together with said drive shaft; a shoe thatslidably contacts said swash plate; a piston slidably disposed inside abore defining a compression space; and a shoe pocket formed as anintegrated part of said piston, which slidably fits with said shoe,characterized in; that a beveled portion is formed at an edge of anopening at said shoe pocket.
 2. A swash plate compressor according toclaim 1, characterized in; that a recessed portion of said shoe pocket,at which said shoe is received is formed so as to achieve a constantcurvature and a projecting portion of said shoe, which faces oppositesaid recessed portion, is formed so as to achieve at least two differentcurvatures; and that a tangent point of said beveled portion and saidrecessed portion is set within a range over which said projectingportion and said recessed portion achieve contact with each other.
 3. Aswash plate compressor according to claim 2, characterized in; that saidbeveled portion is constituted with a curved surface achieving aconstant curvature which is smaller than the curvature of said recessedportion.
 4. A swash plate compressor according to claim 2, characterizedin; that said beveled portion is constituted with a curved surfacehaving at least two different curvatures.
 5. A swash plate compressoraccording to claim 2, characterized in; that said beveled portion isconstituted with a flat surface.
 6. A swash plate compressor accordingto claim 3 or 4, characterized in; that the angle formed by a tangentialline of said recessed portion and a tangential line of said beveledportion at said tangent point is equal to or smaller than 45°.
 7. Aswash plate compressor according to claim 5, characterized in; that theangle formed by a tangential line of said recessed portion and saidbeveled portion at said tangent point is equal to or smaller than 45°.